1. Field
Apparatuses consistent with exemplary embodiments relate to an active optical device in which phase modulation may be easily performed.
2. Description of the Related Art
Optical devices, such as a lens, a mirror, and a prism, are variously used to change a path of light in optical systems. In general, when light passes through an optical device, a phase velocity of the light is changed. The phase velocity is determined by a refractive index of a material. Accordingly, a phase of light is changed by the refractive index, and thus, a path of the light is changed. Based on such a principle, if a shape of a material having the same refractive index changes, a traveling speed of light at each part of the material changes, and thus, a traveling direction of the light changes.
If a refractive index is different for each pixel, a path of light may be easily controlled. Since the path of light may be controlled, new optical characteristics, which may not be obtained in a general optical device, such as a lens, may be obtained. A representative example thereof is a hologram.
An existing optical device that modulates a phase uses a liquid crystal (LC) material. However, in the liquid crystal, if an interval between pixels is decreased, an electric field distribution of an area far away from an electrode is decreased. Accordingly, it is difficult to increase a degree of change in a refractive index of the liquid crystal. Thus, research has been conducted into the development of an active optical device that has high resolution and in which phase modulation may be easily performed.